1. Field of Invention
The present invention relates to an optical disc system. More particularly, the present invention relates to a method of stopping the spindle motor of an optical disc system.
2. Description of Related Art
Multimedia storage is an important aspect in operating a multimedia system through a computer system. Technologists spend a lot of research money on multimedia storage to increase storage capacity and access reliability. Different types of multimedia storage systems all having rather high stability and storage capacity are developed. Since optical disc storage has many advantages including high stability and storage capacity, optical disc products enjoy an ever-increasing range of applications.
In general, two principle modes for operating an optical disc system are the constant linear velocity (CLV) mode and the constant angular velocity (CAV) mode. In the constant angular velocity mode of operation, when data needs to be read out from an optical disc, rotation speed of a spindle motor driving the optical disc remains constant whether the pick-up head is located on an inner section or an outer section of the optical disc. However, the circumference is considerably greater for a circle in the outer section of the optical disc than a circle on the inner section of the optical disc. Hence, a higher data transmission rate is required when the pick-up head is reading from a location close to the outer section of the optical disc compared with a location close to the inner section of the optical disc. Due to the different data transmission rate between the inner and outer sections of an optical disc operating in a constant angular velocity mode, synchronous signal obtained from a data read-out frame can no longer be used for controlling the rotation of the spindle motor. Instead, a frequency generator (FG) is used to provide a frequency signal to detect the rotation speed of the spindle motor, thereby controlling the rotation speed of the spindle motor.
To read data from an optical disc operating in the constant linear velocity mode, rotation speed of a spindle motor driving the optical disc is changed according to whether the pick-up head is located on an inner section or an outer section of the optical disc. Hence, the pick-up head is able to receive data at a constant data transmission rate no matter if the pick-up head is reading data from an inner section or an outer section of the optical disc. In other words, the spindle motor will spin faster when the optical pick-up head needs to read data from an inner section of the optical disc. Conversely, the spindle motor will spin slower when the optical pick-up head needs to access data from an outer section of the optical disc. The rotation speed of the spindle motor is controlled through the synchronous signal from a data read-out frame instead of a frequency signal provided by a frequency generator. However, to stop the rotating spindle motor in the optical disc system (for example, after pressing the eject button), FG signal can no longer be relied on for monitoring whether the spindle motor has already stopped or not.